Pituitary growth hormones: further evidence for evolutionary conservatism based on immunochemical studies.

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Abstract
Immunochemical relatedness of preparations of purified somatotropins (growth hormones) of somatotropins in pituitary extracts from various vertebrate species was investigated by applying an antiserum to a purified somatotropin from a submammalian species, the snapping turtle. With the exception of monkey somatotropin, all mammalian, reptilian, and avian preparations tested showed reactions of identity or near identity by immunodiffusion studies in agar gel. Radioimmunoassay employing labeled rat somatotropin as a tracer and for standards, revealed that these same pituitary preparations gave steep inhibition slopes that were parallel or nearly parallel to each other. Purified somatotropins or somatotropins in pituitary extracts of subreptilian species, including an amphibian and existing primitive fishes, showed partial yet substantial relatedness to mammalian (ray) or reptilian (turtle) somatotropins by both immunodiffusion and radioimmunoassay. Our evidence indicates that the immunochemical relatedness of somatotropins from various vertebrate species appears to be even closer than has been suggested previously, and that a high degree of conservation of structure occurs during evolution.